I found this video by Jeremy Rivkin on Crooks and Liars, only intended to watch a moment or two to see if it would catch my imagination, and ended up watching the entire vid twice. If you sit back, take the time to just absorb the information (presented in an entertaining animation style), you might arrive at the same conclusion I did: empathy, or the lack thereof, explains our current political differences to a TEE.
Have you ever wondered how it is that some of us can look at the less fortunate, the infirm, or those who are suffering from geopolitical strife or natural disasters with eye toward lending a hand, helping any way we can, while others among us see those individuals as somehow threatening, or deserving of their fate? I call it the "I/Me/Mine" philosophy of life, and it applies whenever you take a close look at conservatives and their policies. Conservatives will respond that this is nonsense, citing studies that show their charitable donations equal or exceed those of progressives. What conservatives don't want to admit is that their generosity tends to be rooted exclusively in taking care of "their own"; their church, their extended families, those of their race, ethnicity, religion. In other words, their "kind".
I've noticed this in family settings when the traditional holiday discussions turn to politics. People who are normally the most generous and loving of folks suddenly turn on their heels and slam an emotional/intellectual door on any notion of empathy for the poor, the downtrodden, the elderly (not all elderly, just old folks who don't share their bloodline or community of friends).
What's missing is an empathy gene, a trigger that kicks in among those of us who feel a sense of community with total strangers in need. That "trigger" doesn't kick in with conservatives. What they feel in response to events or information that others might find compelling is a sense of "It's not my problem" or "I got mine, let 'em get theirs". It's as primal and defensive as anything a cave dwelling troglodyte might have felt a hundred thousand years ago. They are empathetic only for their own, their tribe, their fellow cave-dwellers. Not those assholes in the caves on the other side of the mountain... those are the "others", and need to be watched with suspicion.
How else does one explain the stunning lack of empathy some otherwise well-adjusted modern people display in their economic and political policies? They are incapable of seeing the suffering of others through their own experiences, and unwilling to assist unless there is a compelling reciprocation of benefits for their actions.
Maybe one reason conservative fundamentalists have so much trouble with the theory of evolution is because part of their brain development simply hasn't evolved.
They have a missing empathy gene.